21366401 has 12 divisors (see below), whose sum is σ = 24962580. Its totient is φ = 18234720.

The previous prime is 21366391. The next prime is 21366403. The reversal of 21366401 is 10466312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 8116801 + 13249600 = 2849^2 + 3640^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21366401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21366403) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12371 + ... + 13991.

It is an arithmetic number, because the mean of its divisors is an integer number (2080215).

Almost surely, 2^21366401 is an apocalyptic number.

It is an amenable number.

21366401 is a deficient number, since it is larger than the sum of its proper divisors (3596179).

21366401 is a wasteful number, since it uses less digits than its factorization.

21366401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1904 (or 1897 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21366401 is about 4622.3804473453. The cubic root of 21366401 is about 277.4877347608.

The spelling of 21366401 in words is "twenty-one million, three hundred sixty-six thousand, four hundred one".